DE2441749A1 - COMPOSITE LAYER MATERIALS - Google Patents

Description

: τ ζ ββηώ

Dr, -ing. '■ ..! 3: ... "'.'. Jr. β Mu η cha η 22, oi-in-iicifetr. 1β

293-23.134Ρ August 30, 1974

1. Norman Lawrence PARR, Surbiton (Surrey), UK

2. The Plessey Company, Limited, Ilford (Essex), Great Britain

Composite layer materials

The invention relates to layered or laminated composites and methods of making them.

Known techniques for joining, for example, a ceramic material with a metal or another ceramic material are based on the wetting of the ceramic surface with the aid of the use a glaze or a flux. The wetting can ζ. B. by Use of a metal oxide can be made, and the two materials will be. then chemically bonded to one another. The formation of such combinations

509811/0792

293- (JX 42l6 / 04) -T-r (8)

It is therefore essential to achieve a sufficiently strong chemical bond dependent, and many ceramic / metal or ceramic / ceramic composites are difficult, if not impossible, to manufacture with an acceptable level of bond strength because of this requirement the chemical bond is to be fulfilled.

The invention is based on the object of providing composite layer materials and to specify a method for their manufacture, according to which ceramic materials can be mixed with metals without being solely dependent on create a chemical bond and alternatively achieve ceramic / ceramic bonds with a wide range of physical properties permit.

The subject of the invention, with which this object is achieved, is a composite layer material with a first and a second main layer, with the characteristic that the first main layer of ceramic material is made by sintering on vitreous or ceramic Has porous surface area generated grains and the second main layer with the first main layer under penetration connected into the pores of the first main layer.

The material of the second main layer is advantageously either metallic or ceramic, the metallic material from the Group selected aluminum, copper, iron, lead, gold, platinum, tin, nickel, steel, stainless steel, bronze, brass and chrome-nickel while the ceramic material can be silicon nitride, aluminum oxide, boron carbide or tungsten carbide.

The granular material to be sintered onto the first main layer is preferably ceramic or glass-like, with ceramic

50981 1/0792

Material from the group silicon nitride, silicon carbide, aluminum oxide, Boron carbide, tungsten carbide and metal silicate or aluminate is chosen.

The granular material and the material are expedient first main layer same.

The invention also relates to a method for producing such a composite layer material, having the characteristic that a porous surface area on a first main layer of ceramic material by sintering on glass-like or ceramic grains is formed and that the surface area is filled in its pores by material of a second main layer and thereby the two main layers are joined together.

According to one embodiment of this process, the second main layer is metallic and the pores are filled with the porous Surface area on the first main layer is done by forging or press infiltration.

The invention is explained in more detail with reference to the exemplary embodiments illustrated in the drawing; show in it:

1 shows a vertical cross section of the first main layer a hot-pressed silicon nitride of theoretical density,

Fig. 2 shows a vertical cross section of the first main layer according to Fig. 1 with a firmly adhering porous area made of silicon nitride grains, which with the first main layer through Hot presses are firmly connected,

5098 11/07 9 2

FIG. 3 shows a vertical cross section of the combination shown in FIG with a second main layer of metal that penetrates the pore cavities of the porous area, and

4 shows a vertical cross section of a modified multilayer unit, in which a ceramic body by means of a porous area of hot-pressed grains with another Ceramic body is connected.

In the figures, the same parts are denoted by the same reference numerals. Fig. 1 shows a vertical cross section of a first main layer 1 made of hot-pressed silicon nitride powder.

The silicon nitride can be described in any of a number of known ways Gain manufacturing processes including the nitration of silicon powder, such. B. in GB-PS 887,942 is described. That Silicon nitride is then crushed, ground in a steel ball mill, washed with dilute hydrochloric acid and with water and finally dried to a powder. The powdered silicon nitride is then mixed with a flux in powder form, such as. B. magnesium oxide, Lithium carbonate, magnesium nitride, calcium oxide, aluminum oxide, Ferric oxide, calcium nitride, beryllium oxide or beryllium nitride mixed. Then the mixture is placed in a graphite mold and

2 in the mold at pressures of about 2.11 kg / mm and temperatures in the range of 1500 - 1900 C, whereupon the mold is cooled leaves. A second, deep-pored layer 2 made of silicon nitride grains, which is illustrated in Fig. 2 is then created by forming a layer of crushed, hot-pressed silicon nitride grains Loosely on top of layer 1 and apply the unit for one hour

50981 1/0792

hot-pressing in a graphite mold at a temperature of 1700 C to to connect the grains to the layer 1 without eliminating the continuous porosity in the grain layer 2. The size of the used Grain is graded or sized depending on the required physical properties of the composite sheet material. A third method step, the effect of which is illustrated in FIG. 3 is now carried out, whereby a metal is heated to a temperature slightly below its melting point and over the free surface the grain layer 2 is distributed in the graphite mold under slight pressure, so that the metal is layered in the pore spaces of the grains able to diffuse in order to produce a hard or tough metallic outer layer 3 which is firmly connected to the granular layer 2, which in turn is firmly connected to the first high-density layer 1 of hot-pressed silicon nitride powder. A modification of the process provides for a wetting agent, such as titanium hydride, to be introduced into the unit before the formation of the third, metallic layer.

Modifications to the process can be made in order to obtain a certain thickness of the outer layer or the degree of grain to vary in the intermediate layer. The product obtained finds expanse Design application possibilities where highly wear-resistant or contour areas are to be connected with metallic base parts.

A second exemplary embodiment not illustrated in the drawing The invention provides the production of aluminum / aluminum oxide composite sheet materials A layer of recrystallized aluminum oxide with a grain size in the sieve mesh range of 1.68 - 0.841 mm is placed on a piece of dense aluminum oxide ceramic

50981 1/0792

mik at 1600 C with a pressure of 2.11 kg / mm for one hour. This is followed by a layer of aluminum hot-pressed onto the ceramic base, which is porous in or on its surface, for one hour at 600 C with a pressure of 2.11 kg / mm.

Another example of the invention is the production of similarly produced silicon nitride shaped pieces with a granular surface; 5% Silicon nitride containing MgO with a grain size in the screen mesh range of 1.68 to 0.841 mm is hot-pressed to form a dense mass and then crushed into particles, which are then placed on a molded piece of dense, hot-pressed silicon nitride at 1700 C with a

hot-pressed at a pressure of 2.11 kg / mm for one hour. The porous surfaces of these fittings can then be filled or be infiltrated by placing aluminum on it at 600 C.

2
hot-pressing at a pressure of 2.11 kg / mm for one hour. Similarly, one ceramic body can be bonded to another by providing an intermediate layer of pressure sintered grains between the surfaces to be bonded during the hot pressing process. A typical example of this, illustrated in Fig. 4, is the firm bonding of a layer of hot-pressed silicon nitride 1 to a layer of reaction-bonded silicon nitride 4 using an interlayer of silicon carbide grains 5, whereby a strong chemical and mechanical bond is obtained. The layer of grains serving as a link may stand alone or in the presence of a catalyst, such as. B. finely divided silicon nitride powder with or without 5% magnesium oxide can be used.

What the strength of a ceramic / metal composite sheet material

509811/0792

is concerned, this depends in part on the degree of engagement of the metal in the porous layer and partly on the tensile strengths of the metal and the ceramic material. If both strengths are equal, the maximum achievable strength is half as large as that of each of the two components as the cross-sectional area of each component in the infiltrated area is ideally also half. In order to bring the strength of the composite layer materials made of materials with different tensile strengths to the maximum value, the cross-sectional areas of the two materials at the interface should be in inverse proportion to their tensile strength. Similar considerations apply to the creation of a chemical bond between two ceramic materials.

The invention provides a method for predominantly mechanical bonding of two materials and therefore enables the creation of a large one Selection of ceramic / metal composite layer materials possible, which was previously impossible due to chemical incompatibility.

The invention can be used in one respect as a method of producing of a porous area of high specific surface area on the surface of a ceramic material, which area a metallic material can be pressed on so that the metal is pressed into the pores of the porous area, whereby the metallic and the ceramic material interlock with each other. Alternatively the porous area represents an area of high specific surface, which is very good for chemical and mechanical Bonding with another ceramic material is suitable. The criteria For the effective practice of the invention, the granular material, which may be vitreous or ceramic, are selected so that

50981 1/0792

it is suitable for sintering onto the ceramic first main layer, ■ with either the metallic material of the other layer in the porous area can be pressed in or the ceramic material of the second main layer for chemical bonding with the porous area must be suitable. It is clear that these requirements are not a severe limitation, but rather a large group of materials to be fulfilled. Accordingly, the invention is not restricted to the examples explained in detail. Suitable ceramic Materials urrfassen - as mentioned - z. B. silicon nitride, tungsten carbide, boron carbide, silicon carbide, aluminum oxide and magnesium oxide, while ceramic and vitreous materials come into consideration as suitable granular material, with ceramic being particularly suitable Materials e.g. B. silicon nitride, silicon carbide, aluminum oxide, Boron carbide, tungsten carbide and metal silicates or aluminates are. As already mentioned, suitable metallic materials include aluminum, copper, iron, lead, gold, platinum, tin, nickel, Steel, stainless steel, bronze, brass and chrome-nickel.

509811/0 792

Claims (6)

-S- claims 1. composite layer material with a first and a second main layer, "characterized in that the first main layer (l) made of ceramic material one by sintering on vitreous or ceramic grains produced porous surface area (2; 5) and the second main layer (3; 4) with the first Main layer (1) with penetration into the pores of the first main layer connected is. 2. Composite layer material according to claim 1, characterized in that that the second main layer (3) consists of a material from the group aluminum, copper, iron, lead, gold, platinum, tin, nickel, Steel, stainless steel, bronze, brass and chrome-nickel. 3. Composite layer material according to claim 1 or 2, characterized in that that the first main layer (l) made of ceramic material of the group silicon nitride, aluminum oxide, boron carbide and tungsten carbide consists. 4. composite layer material according to one of claims 1 to 3, characterized in that the ceramic grains (2; 5) from the group silicon nitride, silicon carbide, aluminum oxide, boron carbide, Tungsten carbide, metal silicate and metal aluminate are selected. 5. Process for the production of a composite layer material according to 50981 1/0792 One of claims 1 to 4, characterized in that a porous surface area (2; 5) is formed on a first main layer (1) of ceramic material by sintering on glass-like or ceramic grains and that the surface area in its pores is made up of material of a second main layer (3; 4) filled and
thereby the two main layers are connected to one another. 6. The method according to claim 5, characterized in that the second main layer (3) is metallic and the filling of the pores of the porous surface area (2) on the first main layer (l) takes place by forge or press infiltration. 509811/0792